Cal. Gov. Code § 23010.3
Upon adoption of an authorizing resolution by the board of supervisors, in connection with the construction of any sanitary sewer, storm sewer, or drainage improvements, a county may expend any of its available funds for any additional cost of construction of any conveyance works in excess of the construction required for the current project, or for a portion of the cost of conveyance works directly benefiting properties in an area outside the area to be served by the current project, if the board of supervisors first finds and declares in that resolution, that there is an area outside the area to be served by the current project which may in the future utilize the conveyance works; that additional construction of conveyance works for the current project is necessary to serve the outside area in the future; and that the board of supervisors will have the right in the future to use, or to permit the use of, the conveyance works and the additional construction which will benefit the outside area. In lieu of a county contribution of funds for additional construction or for a portion of the cost of the conveyance works where an outside area is directly benefited, the board of supervisors may agree to reimburse, from future connection fees, any entity or person described in subdivisions (a) to (g), inclusive.
The provisions of this section shall be applicable in cases in which improvements are to be constructed by any of the following:
The board of supervisors may impose a connection fee upon any person or district in the outside area to be paid to the county as a condition to connecting to any conveyance works which have been augmented by additional construction, or which have been found by the board of supervisors to directly benefit the outside area, pursuant to this section. The connection fee shall be a prorated share of the total cost of the additional construction, or of the portion of the costs of the conveyance works where an outside area is directly benefited. The fee may include a reasonable amount for administrative costs associated with the collection of the fee and to provide reimbursement to an entity or person described in subdivisions (a) to (g), inclusive. In computing the total cost of the additional construction, or of the portion of the costs of the conveyance works where an outside area is directly benefited, the board of supervisors shall include an amount attributable to interest from the date of completion of the construction to the date of connection and, in the event the board of supervisors agrees to reimburse, from future connection fees, any entity or person described in subdivisions (a) to (g), inclusive, all accrued interest shall be payable to that entity or person.
This section shall not decrease or limit any other power vested in counties or boards of supervisors.
Ca. Gov. Code § 23010.3